PLASMA-DESITY MEASUREMENTS BY MICROWAVE INTERFEROMETER AND LANGMUIR PROBE IN A STEADY-STATE PLASMA COLUMN

摘要

In the paper, a Langmuir probe and a microwave interferometer have been combined to measure the electron density of DC high-voltage discharge of argon in a steady-state plasma column. The two techniques show good agreements with the discrepancy within 20% at pressures of 0.0 1Pa and 0.lPa. With the increasing of pressure, the mean free path of ions ( λ_i ) begins to approach the Debye length (λ_D ) and the collection of ions and indeed electrons become influenced by collisions. At pressure up to 10Pa, the influence of collision cannot be ignored. Electron densities determined from interferometer are 3-5 times than the uncorrected electron densities determined from the Langmuir probe at pressure of 15-30Pa. The corrected electron densities track well with those determined by interferometer. However the values are off by approximately 60%.